Revealing mistake: Steve (Wraith)'s belly appears not to match the rest of the Wraith character's skin tone. Clearly, it is a human body rather than an alien. (00:31:36)
Revealing mistake: When the team lands on the Planet and first step out of the Puddle Jumper, you can see multiple footprints going in and out of the puddle jumper from previous takes.
Answer: Those are actually suits that protect from hazardous chemicals. They are cheaper for the prop department and look nearly the same as biohazard suits. A real biohazard suit would indeed have a helmet that seals to the neck.
Grumpy Scot